Refractory materials are indispensable in a field including a steel manufacturing field in which a high-temperature material is treated. In this field, to make the material thermally more durable is important to stabilize the production of it and to cut the production cost of it. A monolithic refractory material, which is one of refractory materials, has been widely used in view of the merits such as better workability and easy mending.
In manufacturing of the monolithic refractory material, a press with a high pressure that is used in manufacturing of a shaped refractory material is not carried out. Therefore, characteristics of a refractory raw material and a binder are very important. In particular, a calcium aluminate cement (hereinafter, this is referred to as an alumina cement, wherein main chemical components are CaO.Al2O3, CaO.2Al2O3, and 12CaO.7Al2O3) is widely used as a binder.
However, the alumina cement, if it co-exists with Al2O3, shows an expansion tendency when CA2 (CaO.2Al2O3) is formed around 1200° C. Especially, when a large quantity of the alumina cement is added, a crack is caused due to an extraordinary large expansion at high temperature.
In addition, in the insulating monolithic refractory material, the water absorbency of an insulating aggregate (lightweight aggregate) is higher than usual refractory aggregates; and thus, more amount of water needs to be added as compared with usual monolithic refractory materials. Then, the curing strength thereof may be deteriorated thereby leading to a risk of exfoliation when it is removed from a frame.
On the other hand, as to the binder for the monolithic refractory material, beside the alumina cement, a strontium aluminate cement (hereinafter, this is referred to as a strontium cement) has been known. For example, Patent Document 1 discloses the strontium cement comprising the comical composition of SrAl2O4, Patent Document 2 discloses the strontium cement comprising the chemical compositions of SrO.Al2O3, SrO.2Al2O3, and SrO.6Al2O3, and Patent Document 3 discloses the strontium cement comprising the chemical composition of CaxSr1-xAl2O4.
Use of these strontium cements solves the expansion problem at high temperature caused by CA2 formed when the alumina cement is used. Also, the strontium cement exhibits a higher strength than the alumina cement, so that the problematic decrease in the curing strength may be solved as well.